NHTSA Complaint #11711216 — 2012 GMC SIERRA 1500

The contact owns a 2012 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the transmission unexpectedly downshifted, especially between second and third gears. The check engine warning light was intermittently illuminated. In addition, the contact stated that the engine felt as though the engine mounts were inoperable. The contact pulled over to the side of the road and turned off the vehicle. The vehicle was restarted, and the vehicle resumed normal driving. The vehicle was taken to the dealer; however, no cause for the failure was found. The vehicle was not repaired. The contact stated that the failure persisted. The manufacturer was made aware of the failure, but no assistance was offered. The failure mileage was approximately 20,000.